Fire resistant structural units



2 Sheets-Sheef 1 E I B U 0 MAD. m N 0 E .L

April 2., 1957 D. soUBlER ETAL FIR RESISTANT STRUCTURAL UNITS Filed Nov.19, 1952 :llwlliw-4 April 2, 1957 l.. D. soUBlER ET AL 2,787,345

FIRE RESISTANT STRUCTURAL UNITS 2 sheets-Sheet 2 Filed Nov. 19, 1952nue/nim .SoUBmR LEONARDQ EVERETI C. SHUMAN FERR RESESTANT S'RUCTURALUNITS Leonard D. Sonbier and Everett C. Shuman, Toledo, hio, assignorsto Owens-minimis Glass Qompany, a corporation of Ghia ApplicationNovember 19, 1952, Serial No. 321,340

4 Claims. (Cl. 189-34) This invention relates to the production ofstructural units, such as redoors, and in particular to a type of unithaving an initially high resistance to heat and fire and whichresistance increases with a rise in temperature and reaches a maximumunder actual subjection to tire land/ or high temperatures.

ln most lire resistant units, whether wood or steel clad, the structureand core material utilized Will provide a maximum temperature resistancebefore break down and without any change or conversion of the materialwhich will increase that maximum temperature.

This present invention has for its primary object the production of aredoor, or other fire-proof or fire resistant units for various end usesunder high temperature conditions, provided with a core material andcore struc- `ture and other structural features which will provide inthat unit, at or upon installation, a particular temperature resistancerange and which material when subjected to higher temperatures abovethis particular range will undergo a physical and/ or chemical changewhich increases its resistance through still a higher temperatureresistance range.

Une such material is synthetic xonotlite which when subjected totemperatures in excess of 1200c F. undergoes a physical and/or chemicalchange which increases its maximum temperature resistance to at least2000 F.

A xonotlite material undergoes a transformation at a temperature ofapproximately 1400 F., and since in standard lire tests temperatures of1000 F. are reached in live minutes, and continue upward on a curvedline to l700 F. in an hour, and thereafter up to 2000 F. at four hours,such transformation point advances progressively deeper into the corematerial. While with a core made up of individual sections the shrinkagewhen break-down occurs is less than with a monolithic core there cornesa time in the long fire test in which the element or core break-down dueto shrinkage becomes a factor.

Itis important to note that with fire on only one side of the iiredooror other structure, the progressive breakdown of the core material doesnot produce a major structural break-down of the structure as a wholeuntil a substantial length of time has passed. This break-down yoccursin present commercial hredoors in which a type of core material is usedthat can resist only about l300 F. and yet is able toget a fire ratingof one hour when for most of the time the fire temperature is above1300" F. The slow rate at which the break-down occurs progres sivelythrough the particular silicate core used in present commercial redoorsmeans that the over-all structural unit, even though oneface is burnedaway, is still a fire barrier. It is only after this progression of thebreakdown, due to loss of water from the core, has occurred to asubstantial or considerable depth that the structural strength isreduced to a point of virtual failure. In present redoors this occurssometime after one hour.

In the case of a xonotlite core lredoor, or` panel, the subject of thispresent invention, the integrated core of e tates Patent atented Apr. 2,V1957 synthetic xonotlite would go through the i l400 F. transformationto Wollastonite and then present to the tire a material which is capableof resisting temperatures up to at least 200 F. As a result of thistransformation such a door will not show `any significant physical,chemical or structural weakness insofar as the core is concerned for atleast four hours.

The rate or" deterioration due to the shrinkage, after say 2100 F. hasbeen passed, as it progresses through the core is quite slow and thesignificant point is that even though so-called maximum workingtemperatures of the core material are exceeded, there is a time delayfor any possible failure of the structural unit, because the progress ofbreak-down or physical disintegration through the core is very slow.

Since the maximum temperature of a standard hre test is @300 at eighthours in which the temperature has progressed at per hour after the 2000F. at four hours, the door with a synthetic Xonotlite core willwithstand a standard hre test for a period longer than 4 hours insofaras the core is concerned. This would mean that with metals that do notchange 'appreciably in these high temperature ranges that theintegratedXonotlite core should give a lire barrier for a very appreciablyextended length of time. This would also mean that units can be made forservices where high temperatures are encountered over and above the mereprotection against accidental fire.

Other objects of our invention will be apparent from the followingspecification and accompanying drawings.

In the drawings:

Fig. l is a face View of a :structural unit which may serve as a door orpanel, portions of the surface covering or envelope being broken away;

Fig. 2 is a sectional elevational View at the line 2-2 on Fig. l, but ona larger scale and with parts broken away, illustrating the sectionalstructure of the cofre and the Venting arrangement of the envelope;

Fig. 3 is a fragmentary sectional view showing the core restrainingchannel and the enclosing envelope;

Fig. 4 is a part sectional elevational View of a structural unitprovided with a monolithic core;

Fig. 5 is a fragmentary sectional view of another mono lithic structure;and

Fig. 6 is a fragmentary sectional view of a structure wherein theenvelope is comprised of adhered veneers of lire-proofed material.

In practicing our invention there are several practical ways of makingstructural units, such as doors, partitions, etc., capable of hightemperature heat or lire resistance wherein the enveloping material ismetal or other materials highly resistant to re and/or high temperaturesand the core material consists essentially of a silicate cornpound inintegrated form.

For example, a metal case may be provided which is entirely closed, withthe exception of a filling opening and an air vent, and which may befilled with a lime, silica, asbestos or aggregate Aand Water Lslurrycapable of being converted to an integrated crystalline structurewherein the crystals have the chemical formula SCaOjSiOaI-IZO. Uponinduration of the slurry and Vdrying of the product the iill openingissealcd with a low melting point material and the air vent ispermanently sealed. Thus, a structural element is provided having ametal enclosure and a monolithic crystalline structure core of'synthetic xonotlite which is unaffected insofar as chemical compositionis concerned by temperature less than approximately 1400 F.

Secondly, a metal case may be provided and a preindurated and driedXonotlite monolithic core inserted therein and sealed. Also thispreindurated core may be inserted into the metal case in sections withthese sections abutting in vertical and horizontal planes and with the 3abutting edges having articulation, such as a tongue and groove or thelike.

Prefabricated pieces or articulated sections of synthetic Wollastonitemay be inserted and sealed into a metal case. However, we havediscovered that the preconversion of xonotlite slabs or blocks toWollastonite is, from the commercial viewpoint, not a simple matter. Forexample, it requires heating oven equipment capable of providingtemperatures `of at least 1400 F. and adapted for regulable control ofthe drop of temperature to room temperature over an extended period oftime. Without such controls the conversion becomes a risky commercialendeavor because of the stress and strain occuring in the slabs whichresult in breakage of a type which lessens the eiciency of the core inits resistance to the transmission of llame or gases.

Consequently it is the more desirable procedure to retain the core inits unconverted form, xonotlite, in the completed article, so thatconversion will only occur while the core is enclosed in the door orpanel structure and while being subjected to the high temperatures suchfor example, as those incident a fire. In the majority of instances suchhigh temperatures is applied to only one side of the structure and theprogression of the conversion from xonotlite to Wollastonite Willrequire an extended time interval.

Conversion of the xonotlite core to Wollastonite while conned in aretaining enclosure will lengthen lire resisting time interval by thatlength of time which is required to eliminate the predetermined amountof free water contained in the highly porous xonotlite plus the timeintervals required to eliminate the combined water and produce thenecessary atomic rearrangement of the crystals in the change fromWollastonite to pseudowollastonite at approximately 2100 F.

In addition to the above the application of temperatures in excess of2100 F. will require a time interval of some length before the core willreach a point of structural break-down such as to lose its eiciency as afiredoor.

Such delaying of the conversion also reacts to extend the life of thestructural unit in that its final progression to a structural breakdownof the core is greatly delayed.

A preferred structure is one wherein articulated tongued and groovedsections of molded synthetic xonotlite are sealed within a metal caseand wherein the xonotlite has been dried to about 30% at about 300 F.Under such conditions the xonotlite would have both free and combinedwater to lose when subjected to high temperature and the procedure ofconversion to Wollastonite accordingly would be less abrupt through themass.

Further, the tongue and groove construction of such articulated sectionsgives a protection against leakage of gases or flame due to warpage,which protection is not possible with a monolithic structure when itcracks due to warpage or for any other reason.

In Figs. l and 2 there is shown one form of a metallic casing structurewhich may be utilized for producing structural units, panels or doorshaving either a monolithic or articulated core structure. In thisparticular structure, a channel member extends completely around theperiphery of the core 16. One of the major or face surfaces of the doorunit is formed by a sheet or stainless steel or similar alloy 11covering the side of the door and the opposite side is formed With acarbon steel face 12. However, both faces may be of the same material asshown in Fig. 4 and be interconnected by a metal strip 11b and seamwelded at 12b.

The sheet 11 has its marginal portions 11 turned inwardly in the form offlanges which overlie the .channel 10 and form the major portion of theedge surfaces 20 of the door. The face plate 12 is formed with marginalanges 12a which complete the edge surfaces 20. and abut the anges 11aalong the weld line 12b. Y

Vents 13 and 14 are provided respectively in the top and bottom surfacesof the door and are normally sealed with plugs 15 of low melting pointmaterial, such as, some metal which will melt at or below the boilingpoint of water, for example, Cerra Matrix Metal. The purpose of sealingthe vents 13 and 14 is to prevent the core 16, after being formed orplaced in the steel casing, from picking up additional moisture,although where conditions make it desirable the vents may be left opento deliberately permit the porous integrated core 16 to pick upadditional moisture. In any event the ultimate purpose of the vents isto permit the escape of steam vapors when the door is subjected to hightemperatures.

In the preferred form as mentioned above, the core 16 is preferablyinitially formed of the crystalline compound xonotlite, in integratedporous form having a density of approximately 10 p. c. f. to about 35 p.c. f. or to greater or lesser densities as the end use may dictate, andthat said core is in sections having tongue 17 and groove 18articulations with each other extending horizontally and if necessaryalso vertically.

Such a core 16 when subjected to sufiiciently high temperatures losesboth its free and combined water. When the door is in use and a fireoccurs by which it is subjected to such high temperature, the heatusually being applied mainly to one side of the door, there is a strongtendency to Warpage and resultant cracking of the core material. Thearticulation being of the tongue and groove type prevents such crackingand the resultant leakage of heat and gases through the thickness of thedoor. Such leakage could not ordinarily be prevented in a monolithicstructure when it cracks.

In this type of fredoor, regardless of whether the core 16 is of themonolithic or articulated type, it is necessary to make provision in thestructure to olset the shrinkage which will occur when the syntheticxonotlite core is subjected to these high temperatures. For example, ifthe door is subjected to a temperature sufficiently high to cause thexonotlite to convert to synthetic Wollastonite, there will be anover-all shrinkage in the length, width and thickness of the core. Byproviding a heat retarding element such as the channel structure 10around the periphery of the core 16 or some similar means vacant spacedue to any such shrinkage will automatically remain enclosed and abarrier to the transmission of heat provided.

With respect to the tongue 17 and groove 18 portions, these are of suchdepth and Width that it would be necessary for all three legs or splinesthereof to be broken ot in order to permit the excessive passage ofheat, etc. The total shrinkage in a door of usual Width will beapproximately 1A" and with the channel 10 extending completely aroundthe door there will be no possibility of direct leakage of excessiveheat or tlame. However, it is possible to control this shrinkage factorto some considerable extent by providing the proper combination ofporosity or density in the core as well as the thickness of the core tosuit particular or specific conditions of heat exposure.

Earlier in this disclosure it was mentioned that one side of this dooris faced with a stainless steel facing 11 and that this facing extendsover the major portion of the edges 20 of the door. There is nothingunique in this in itself but it has significance in connection with therest of the construction. The sheet on the inside, or cold side in afire test, is a 24 gauge carbon steel sheet 12. The stainless steelsheet 11 may be approximately .008" in thickness. Y

The stainless steel sheet 11 has a lower conductivity than a carbonsteel sheet of the same thickness, is made of a thinner gauge sheet andthe thinner gauge lower conductivity sheet covers most of the edge. Mostimportant, steel angles or channels 10 (Figs. l and 2) and steel angles26 (Figs. 4 and 5) are built into the panel to approach close to thestainless steel sheet 11. Their conductivity is Ialso higher than thatof thestainless steel sheet 11 (per cross sectional area). These angles10 arsenite and 2,6 are in intimate contact with the carbon-steel sheet1.2 on the reverse side. It is presumed that 'the amount of heat thatcan be conducted by the stainless steel sheet 11 at the temperatures.reached will be distributed rather rapidly through the greater mass. ofsteel designed on the inside of these panels and through them will befed rather rapidly to the carbon steel sheet 12 on the inside. Theemissivity of a black carbon Asteel sheet is high.

The basic feature herein disclosed comprises the building of a iredooror other unit having a core 16 which is normally resistant to specifictemperatures, namely, approximately 1200" F., and which when subjectedto higher temperatures will inherently increase its. .resistance to amuch higher range of temperatures due to the change in physical and/orchemical forni and/or thev atomic rearrangement of the crystals formingthe porous. integrated core 16.

A monolithic form of core 16 as shown in Figs. 4 and 5 may also be madeand utilized as follows:

A hollow fircdoor case 25, made of a carbon or other steel or othermetals or combinations thereof, with a melting point of from 1800Q F. to2500 F., is so designed as to encompass all surfaces of the door, and isformed with a lill opening 13 in one of the edge surfaces 20, throughwhich a xonotlite slurry is poured to fill said case. Vents 27 and 28are also provided to obviate air entrapment and these are welded closedafter induration of the slurry.

This filled case is then placed in an indurator, with the pouringopening 13 still open, and is subjected to a pressure and temperatureand for a time interval Suthcient to convert the slurry to an integratedmonolithic structure of a crystalline compound, the crystals of whichhave the formula 5CaO.5SiO2.H2O. This door is then placed in a drier andthe free water is evaporated, for example, down to approximately 30% 300F. The pouring opening 13 in the door may, if desired, be then sealedwith a slug 15 such as lead or other low melting point material toprevent any moisture pick-up by the xonotlite core. We now have a steeliiredoor in which the core 16 (xonotlite) has a normal iire resistanceup to approximately 1400 F. without any structural change eitherchemically or physically. However, by maintaining exposure to a somewhathigher temperature the xonotlite will convert to synthetic Wollastoniteat approximately l400 F. (760 C.) and then be chemically unaffected upto approximately 2100o F. As the temperature is further increased beyond1400 F., the Wollastonite will become pseudowollastonite atapproximately 2l00 F. (ll50 C.). From this point on the effect offurther temperature increase upon the core 16 is that it may begin agradual structural break-down and nally melt when the temperaturereaches 2800 F. (l540 C.). The above structural changes take placewhether the core be monolithic or of articulated sections. Angle shapedmembers 26 extend around the inside of the case 25 to act as barriers tothe heat transfer when the core 16 shrinks.

From the preceding it should be quite apparent that a firedoor has beenproduced the core 16 of which, at its initial production, has apotential re resistance in the proximity of at least 1200 F. withoutstructural change, but when subjected to actual re or high temperatureconditions the resistance of said core 16 progressively increases atleast another 1000 F. and has a final potential resistance at Iatemperature of at least 2l00 F. but probably not greater than 2800 F.except for short intervals of time. During the above procedure oftemperature change the crystals of the core structure 16 will changetheir chemical formula from Ca0.SiOa

Many ferrous 0r non-ferrous metals or combinations thereof may be usedas the envelope for the core and possibly Some non-metallic materialssuch` as reproofed wood veneers, etc.

The core materials to be utilized in carrying out this invention are tobe of the crystalline compound yform having the formula SCaO.5SiO2.H2,Oand to be in integrated form and having a density Ialways substantiallyless than that of the natural mineral xonotlite. The density of theproduct will of course. be always dictated by the specific temperaturecondition to be coped with in any specific installation.

The lath-like microcrystalline structure utilized in this invention isof great value as insulation in the high temperature eld and tests todetermine its applicability in- -dicate it will withstand excessivelyhigh temperatures for long periods of time without breaking ordisintegrating.

For example, this material at 20# density, was subjected to a series oftests wherein the surface temperature, from direct flame application,reached approximately 2000 F. and after two hours of exposure theretowas subjected to a stream of cold water under pressure withoutshattering and with only superficial surface cracking.

The shrinkage of this material is extremely low when compared to otherlime-silica products and its hardness of 6.5 according to Mohs scale,together with its quality of withstanding extreme thermal shock uponquenching makes it a most desirable product for many purposes and inparticular for fire resistant structures. Such a product, because of itsrigid structure lends itselfv to various forms or methods of finishing,such as shaping, cutting and sawing as well as the polishing of itssurfaces to very smooth finish.

In Fig. 6 there is illustrated a structure wherein the channel 10 whichmay be metal or any fire resistant material, such as, reproofed wood,and which extends entirely around the core 16 to thereby function bothas a retaining element for the core 16 yand a heat barrier as the coreshrinks when subjected to high temperatures. Actually the member 10 maybe of various shapes and forms provided it supplies the desirablebarrier feature.

T he core 16 may be of either monolithic in form or comprised ofsections either in abutting or articulated arrangement. A iireproofedveneer crossband 30 is adhered to both faces of the core 16 and thoseedges 10B of the channel 10 which are parallel with the faces of thecore 16. This assembly is covered over with a inishing veneer oftreproofed wood 31 adhered to crossband 30. A facing 32 yof reproofedWood veneer may extend completely around the outer edges 20 of thestructure as a nishing means or covering.

Modifications may be resorted to within the spirit and scope of theappended claims.

What we claim is:

l. A structural unit having a high resistance to iire and heat at atemperature of approximately 1200o F. comprising an outer ireproofenvelope having a vent on the surface thereof sealed with a substancehaving a low melting point, and a highly porous integrated corecornpletely filling said envelope, said core being a hydrous calciumsilicate crystalline compound whose crystals have the formula5CaO.5SiOz.H2O, said core having free water therein, said structuralunit having the property of increasing its resistance to tire and heatto at least 2000 F. upon being subjected to a temperature ofapproximately l400 F., said vent being opened when the sealing substancetherein is heated above its melting temperature to permit water vapor toescape through said vent, said core being converted to Wollastonite at atemperature of approximately 1400 F., said Wollastonite having theproperty of increasing the resistance of said structural unit to atemperature of at least 2000 F.

2. The structural unit defined in claim l, wherein the 7 outer reproofenvelope is of metal and the substance sealing the vent is lead.

3. The structural unit defined in claim 1, wherein said core consists ofarticulated tongued and grooved sections, each section being ininterlocked relationship with each adjacent section.

4. A structural unit having a high resistance to fire and heat at atemperature of approximately 1200 F. comprising an outer reproofenvelope having a vent on the surface thereof sealed with a substancehaving a low melting point and a highly integrated core in sectionalform filling said envelope, each of said sections of said core being ahydrous calcium silicate crystalline compound whose crystals have theformula 5CaO.5SiOz.H2O, said core having free water therein, a heatbarrier channel member in abutting relation with and completelysurrounding the peripheral edges of said core, said structural unithaving the property of increasing its resistance to fire and heat to atleast 2000 F. upon vbeing subjected to a temperature of approximately1400 F., said vent being opened when the sealing substance therein isheated above its melting temperature to permit water vapor to escapethrough said vent, said core being converted to Wollastonite at atemperature of approximately 1400 F., said Wollastonite having theproperty of increasing the resistance of said structural unit to atemperature of at least 2000 F.

References Cited in the tile of this patent UNITED STATES PATENTS

1. A STRUCTURAL UNIT HAVING A HIGH RESISTANCE TO FIRE AND HEAT AT ATEMPERATURE OF APPROXIMATELY 1200*F. COMPRISING AN OUTER FIREPROOFENVELOPE HAVING A VENT ON THE SURFACE THEREOF SEALED WITH A SUBSTANCEHAVING A LOW MELTING POINT, AND A HIGHLY POROUS INTEGRATED CORECOMPLETELY FILLING SAID ENVOELOPE, SAID CORE BEING A HYDROUS CALCIUMSILICATE CRYSTALLINE COMPOUND WHOSE CRYSTALS HAVE THE FORMULA5CAO.5SIO2H2O, SAID CORE HAVING FREE WATER THEREIN, SAID STRUCTURAL UNITHAVING THE PROPERTY OF INCREASING ITS RESISTANCE TO FIRE AND HEAT TO ATLEAST 2000* F. UPON BEING SUBJECTED TO A TEMPERATURE OF APPROXIMATELY1400*F., SAID VENT BEING OPENED WHEN THE SEALING SUBSTANCE THEREIN ISHEATED ABOVE ITS MELTING TEMPERATURE TO PERMIT WATER VAPOR TO ESCAPETHROUGH SAID VENT, SAID CORE BEING CONVERTED TO WOLLASTONITE HAVING THEOF APPROXIMATELY 1400* F., SAID WOLLASTONITE HAVING THE PROPERTY OFINCREASING THE RESISTANCE OF SAID STRUCTURAL UNIT TO A TEMPERATURE OF ATLEAST 2000*F.